Syntheses of Chromium Pentacarbonyl Derivatives of Arsenic(V) and Antimony(V). Contrasting Chemical Reactivity with Organic Halogen Derivatives

We have synthesized a new series of chromium−group 15 dihydride and hydride complexes [H2As{Cr(CO)5}2]-
(1) and [HE{Cr(CO)5}3]2- (E = As, 2a; E = Sb, 2b), which represent the first examples of group 6 complexes
containing E−H fragments. The contrasting chemical reactivity of 2a and 2b with organic halogen derivatives is
demonstrated. The reaction of 2a with RBr (R = PhCH2, HC⋮CCH2) produces the RX addition products
[(R)(Br)As{Cr(CO)5}2]- (R = PhCH2, 3; R = C3H3, 4), while the treatment of 2b with RX (RX = PhCH2Br or
HC⋮CCH2Br, CH3(CH2)5C(O)Cl) forms the halo-substituted complexes [XSb{Cr(CO)5}3]2- (X = Br, 5; X =
Cl, 6). Moreover, the dihaloantimony complexes [XX‘Sb{Cr(CO)5}2]- can be obtained from the reaction of 2b
with the appropriate organic halides. In this study, a series of organoarsenic and antimony chromium carbonyl
complexes have been synthesized and structurally characterized and the role of the main group on the formation
of the resultant complexes is also discussed.